1. Field of the Invention
Embodiments of the present invention generally relate to a mechanism for conditioning a polishing surface in a chemical mechanical polishing system.
2. Description of the Related Art
Chemical mechanical polishing is one process commonly used in the manufacture of high-density integrated circuits. Chemical mechanical polishing is utilized to planarize a layer of material deposited on a semiconductor wafer by moving the substrate in contact with a polishing surface while in the presence of a polishing fluid. Material is removed from the surface of the substrate that is in contact with the polishing surface through a combination of chemical and mechanical activity.
In order to achieve desirable polishing results, the polishing surface must be dressed or conditioned periodically. One type of conditioning process, typically performed on polyurethane polishing pads traditionally utilized in chemical mechanical polishing, is configured to restore the fluid retention characteristics of the polishing surface and to remove embedded material from the polishing surface. Another type of conditioning process, typically performed on fixed abrasive polishing material, is configured to expose abrasive articles disposed within structures comprising the abrasive polishing material, while removing asperities from the upper surface of the polishing material and leveling the structures comprising the polishing surface to a uniform height.
In one embodiment, a polishing surface conditioner includes a replaceable conditioning element, such as a diamond disk, coupled to a conditioning head that is movable over the polishing surface. The diamond disk is lowered into contact with the polishing surface while being rotated. The conditioning head is generally swept across the rotating polishing surface to allow the diamond disk to condition a predefined area.
Conventional conditioners commonly utilize diaphragms to force the conditioning head against the polishing surface during conditioning. Typically, more force is applied near the centerline of the diaphragm, while less force applied at the perimeter of the diaphragm which is fixed to a housing. As fixed abrasive polishing material is relatively soft as compared to conventional polyurethane polishing pads, the non-uniform force applied to the polishing surface by the conditioner may result in uneven conditioning.
Moreover, care must be exercised while moving the conditioner over the polishing material to avoid inadvertent contact between the conditioning head and the fixed abrasive polishing material which may result in gouging or otherwise damaging the polishing material. If the vacuum applied to the diaphragm holding up the polishing head is disabled, or the diaphragm fails, the polishing head will suddenly drop, causing the conditioning head to collide with the polishing surface. Collision between the conditioning head and polishing surface generally result in damaging at least the polishing surface or the conditioning head. Once the polishing material is damaged, that section of the polishing material must be discarded (i.e., not used for polishing) thereby disadvantageously reducing the number of substrates that may be polished per unit quantity of polishing material, resulting in decreased throughput and an increased cost of consumables (e.g., the polishing material).
Therefore, there is a need for an improved conditioning mechanism.